The purpose of this study is to demonstrate the feasibility of anaerobic treatment of pharmaceutical and baker's yeast industry effluents in a joint treatment system. Anaerobic treatability studies have been performed in a lab-scale upflow anaerobic sludge blanket reactor (UASBR). The experimental study has been carried out for 333 days. The influent COD's during the experimental study were about 10,000 mg/l. Pharmaceutical wastewater has a 5% of inhibition on the COD removals at the dilution rate of 1/100 or more in the joint anaerobic treatment with baker's yeast industry effluents. Maximum inhibition of 10% on the average was observed when the system was characterized with acclimation periods. The study has shown that, following the solvent extraction with pre-aeration process, a common anaerobic treatment can be applied to baker's yeast industry wastewater and to pharmaceutical industry effluents. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.